The Spain midfielder suffered a suspected anterior cruciate knee ligament injury, which could rule him out for much of the season
Pep Guardiola fears Javi Martinez will be out for a considerable length of time after suffering a serious looking knee injury in Bayern Munich's 2-0 DFL Supercup defeat to Borussia Dortmund.
His attempt at an acrobatic volley during the first half saw his leg connect with Marcel Schmelzer in awkward fashion, resulting in him being stretchered from the field.
Guardiola, who claimed to only have a handful of fully fit players before the game, was pessimistic in his assessment of the problem.
"The bad news is the injury to Javi Martinez," he said. "He was in good shape.
"We'll know what he's got tomorrow [Thursday]. But I think that he will be out for a long time."
Guardiola selected a mixture of first-team stars and inexperienced youngsters, with many players still recovering from a gruelling World Cup campaign with Germany.
One of those was Philipp Lahm, who was introduced at half-time for Thomas Muller, and the 30-year-old conceded it had been a tough task with so many regulars either unavailable or not at 100 per cent.
"We were missing a lot of players and we're still finding our feet in pre-season," he said. "It was difficult."